"James Salisbury" nntp.dsl.pipex.com wrote in message
...
Dave Liquorice wrote:
On Sat, 13 Mar 2010 23:53:35 +0000, tony sayer wrote:

Yes I did read about that somewhere, seems the earth at that sort of
voltage and DC was quite suitable for that purpose....

The impedance of The Earth is effectively zero, making good
connection to it is the tricky bit. In the days of trams and traction
power return via the tracks they initially weren't very bothered
about making sure the tracks had decent electrical continuity. The up
shot being that the traction power would find the path of least
resistance, sometimes down the lead sheaths of telephone cables
buried near by until the GPO started making a fuss.

It is still a modern problem, the CERN tunnels do suffer from surface
traction current ingress....

You would have thought they would have put mesh in the walls to act as a
faraday cage.